A. Chorionic gonadotropin:
This hormone is produced during pregnancy and supports the corpus luteum but is not involved in male secondary sex characteristics or spermatogenesis.

B. Progesterone:
Progesterone is a female hormone involved in preparing the uterus for pregnancy, not male sexual development or sperm production.

C. ACTH:
Adrenocorticotropic hormone stimulates the adrenal cortex to produce cortisol; it does not affect male sex characteristics.

D. Testosterone:
Testosterone is the main male sex hormone responsible for sperm formation and the development of male secondary sex characteristics.

A. During labor, pressure of baby's head on cervix stimulates release of oxytocin:
This is a classic example of positive feedback-oxytocin increases uterine contractions, which increase pressure and stimulate more oxytocin release.

B. Menstrual cycle:
The menstrual cycle involves both positive and negative feedback mechanisms, but is not a pure example of positive feedback.

C. Blood glucose regulation:
This is an example of negative feedback involving insulin and glucagon.

D. Wake/sleep cycle:
This is regulated by circadian rhythms, not primarily a feedback loop of endocrine hormones.

A. Erythropoietin:
Erythropoietin is released by the kidneys in response to hypoxia to stimulate red blood cell production.

B. Renin:
Renin is secreted in response to low blood pressure, not low oxygen levels.

C. ADH:
ADH responds to high plasma osmolality and low blood volume, not oxygen levels.

D. Aldosterone:
Aldosterone is secreted in response to low sodium or high potassium, and part of the RAAS, not oxygen deficiency.

A. Diaphoresis:
Excessive sweating is more common in hyperthyroidism due to increased metabolism.

B. Protruding eyeballs:
Exophthalmos is associated with Graves' disease (hyperthyroidism), not hypothyroidism.

C. Weight gain:
Hypothyroidism slows metabolism, often resulting in weight gain.

D. Palpitations:
Palpitations are more common in hyperthyroidism due to increased sympathetic activity.

A. Urethra:
The urethra is the passageway for urine and semen but not where sperm matures.

B. Vas deferens:
The vas deferens transports mature sperm but does not play a role in maturation.

C. Ejaculatory ducts:
These ducts conduct sperm to the urethra but do not aid in maturation.

D. Epididymis:
The epididymis is the site where sperm mature and are stored.

A. Prolactin:
Prolactin promotes lactation, not growth.

B. Thyroid-stimulating hormone (TSH):
TSH regulates the thyroid gland but is not the primary growth hormone.

C. Growth hormone (GH):
GH, secreted by the anterior pituitary, stimulates growth in bones and tissues.

D. Adrenocorticotropic hormone (ACTH):
ACTH stimulates the adrenal cortex, not growth.

A. Early onset of menstrual cycle:
While it may affect long-term reproductive health, it does not cause sterility.

B. Torn hymen:
A torn hymen does not affect fertility.

C. UTI (urinary tract infection):
While painful, a UTI does not cause infertility.

D. Repeated episodes of untreated sexually transmitted infections:
Untreated STIs can lead to pelvic inflammatory disease (PID), scarring, and infertility.

A. Causes Na+ and water reabsorption:
Aldosterone increases sodium (and water) reabsorption in the kidneys, which raises blood volume and pressure.

B. Depletes blood volume:
Aldosterone helps increase blood volume.

C. Causes K+ reabsorption:
Aldosterone promotes potassium excretion, not reabsorption.

D. Cause Na+ excretion:
Aldosterone causes sodium retention, not excretion.

A. Low blood volume:
This stimulates ADH and aldosterone, not insulin.

B. Low blood levels of calcium:
This stimulates parathyroid hormone (PTH), not insulin.

C. High blood levels of glucose:
Insulin is secreted by the pancreas in response to elevated blood glucose to facilitate cellular uptake of glucose.

D. High blood levels of potassium:
Though insulin helps drive potassium into cells, its release is primarily stimulated by glucose.

A. Are secreted in response to decreasing blood glucose levels:
Only glucagon is secreted when glucose is low; insulin is secreted when it is high.

B. Elevate blood glucose levels:
Only glucagon elevates blood glucose. Insulin lowers it.

C. Secreted by the beta cells of the islets of Langerhans:
Only insulin is secreted by beta cells. Glucagon is secreted by alpha cells.

D. Are secreted by the pancreas and are concerned with the regulation of blood glucose:
Both hormones are secreted by the pancreas and work together to regulate blood glucose levels- insulin lowers it, and glucagon raises it.